Everyone who has gazed at Mars with the dream of settling there has always pondered the idea of terraforming the world. That is to say, can we turn
Mars into a second Earth, or close enough, so that people can walk the surface of the planet without spacesuits and live like we do here on Earth.
There have been many science fiction stories written on the subject and, even though I don't care for the books, one of the highest among them is Kim
Stalney Robinson's Red Mars trilogy.
More recently, Elon Musk and other have suggested terraforming Mars as well. It makes sense from the POV of giving humanity a second home and also
from the POV of all that extra room. Mars has the same surface area as the land area of the Earth, more or less, and even with oceans covering 60% of
the surface after terraforming, that's a lot of new land for the taking. it would never be as balmy as most of Earth, but it would be a new world
free of worries whether or not someone else is getting squished when you settle the land. Call the New World Guilt Free.
Reality, however, has a way of interfering with one's dreams: there has been some recent results that have been...less than encouraging.
There are two really big issues for terraforming Mars (so far). The first was first that the Phoenix lander and then the Curiosity rover found that
the planet has a LOT of perchlorates
in the soil. By weight, they appear to be .5%. That
doesn't sound like alot, but perchlorates are toxic
to people. Mars is far
beyond a superfund site and having kids there would be beyond risky.
The second problem was known, but not confirmed to be as bad as it is..until now. Mars lost its atmosphere. Folks originally thought it had been
sequestered in the rocks in the form of carbonates. It wasn't.
New research shows that Mars actually outright lost its atmosphere. It was not sequestered. The total amount of carbon dioxide sequestered, whether
in the ice caps or in the few carbonates found, will only raise the atmospheric pressure on Mars to about 7% of earth sea level. That's the
equivalent, roughly, of being at 61,000 feet here on Earth. Pressure suits are still required.
To fix this, any would be terraformer will need to bring in something the size or mass of a large
object. Something like Quaoar
would work. Comets are simply too small. However, getting a Kuiper Belt Object to Mars will require insane amounts of energy and you better do it
both gently and not miss. Something that big wandering around the Inner Solar System would be...disastrous.
Even then, once you have an ocean and atmosphere, you have a toxic mess to clean up. Those perchlorates are going to react with all the nonwater
volatiles you brought in: Mars is, in many ways, the Clorox Planet. And what did your parents say about mixing ammonia and bleach? yeah. Now
imagine on a planetary scale. That will require importing ridiculous amounts of raw sodium (as in the metal) to produce salts and also lots and lots
of the bacteria (which I hope will survive in that atmosphere) that process the perchlorates.
Mars is going to be tough to terraform, no matter what.